1. Field of the Invention
The invention relates to self-adhesive, expandable silicone compositions, to their preparation, and to the materials obtained by expansion and crosslinking.
2. Description of the Related Art
Self-adhesive silicones are a challenge to the developer, since the surface energy and morphology of silicones means that they tend to be inert with respect to adhesion. Consequently there are only a few studies on this topic in which the silicone composition is modified in an attempt to impart adhesion to the silicone polymer (polysiloxane) in order to avoid preliminary work which is laborious and is hampered by uncertainties, such as, for example, pretreatment, priming, etc., as disclosed in specifications EP 1 106 662 B1, EP 0 686 671 A2, and EP 0 875 536.
The automatic production of silicone foam composite articles—that is, of parts which come about through automatic adhesion of expanded silicone to the support material—is desirable from the standpoints of economy and environment (no solvent load as a result of primers; energy saving), but has not been successfully achieved to date. There are a number of reasons for this.
1. The development of voids (bubbles) hinders the migration of adhesion promoters to the support (substrate) surface, which is necessary for the development of adhesion, or greatly prolongs, and at the same time narrows, the migration pathway.
2. The development of bubbles also weakens the area of contact at the substrate contact area, and massively reduces the possible surface area for the development of adhesion.
3. In many cases, the blowing agents used for expansion enter into chemical and/or physical interaction with the adhesion promoters, and, as a result, their effect is negatively influenced.
In the apparel and textile industries, for the purposes of insulation and of protection, expanded laminates or inserts are frequently used for the manufacture of products.
These inserts or laminates of functional clothing, with properties of insulation or of shielding in some other way, are nowadays manufactured most commonly from foamed chloroprene rubber (CR hereinbelow), also known under the name Neoprene®. CR is an organic rubber containing halogen (chlorine). On account of this, its decomposition or degradation is accompanied by release of toxic hydrogen chloride. Chloroprene, moreover, is vulcanized using intensely odorless and highly chemically reactive—that is, controversial—crosslinkers. The complete removal of the latter or the full removal of the by-products from the vulcanisate (rubber) is chemically and physically impossible. The expansion (foaming) of chloroprene likewise takes place using chemically reactive, intensely odorous, and controversial agents. The removal of the by-products is likewise not completely possible.
Nevertheless, CR is employed above all as a foam in functional clothing, such as diving, swimming, and surfing suits, motorcycle clothing, climbing clothing, skiwear and protective clothing, etc. In these applications, the advantages of CR foam include the following:                relatively good ozone resistance;        relatively good salt water resistance;        lightweight foam;        acceptable stretch;        low production costs.        
In the absence of functioning alternatives, all of the disadvantages of CR in these applications are tolerated:                the CR compositions are not free of odor when stored, for example, at slightly elevated temperature; in enclosed spaces, as in an automobile, for example, highly unpleasant odors are given off;        the CR compositions are not free from reaction derivatives of the vulcanization and expansion;        the CR compositions are not very resistant to combined, typical outdoor influences such as UV, heat, and cold;        stabilization against light exposure and heat exposure is possible only with the aid of questionable stabilizers such as loss stabilizers;        attainment of low, highly stretchable hardness only with the aid of plasticizers, and consequent reduction in resistance and other mechanical parameters;        mechanically moderate physical property levels with high permanent deformation and hence high tension and compression set;        low dynamic resistance to combined loading, as in the case of crease loading or tensile loading under heat, under cold, or under exposure to media;        limited waterproofness, since not water-repellent;        unpleasant to wear for any duration, on account of very low gas permeability and vapor permeability (U.S. Pat. No. 7,078,453, indeed, describes their use as a gas barrier; they are therefore not breathable, and hence there is accumulation of sweat);        production of dense, toxic, halogen-containing smoke in the event of fire; less combustible versions possible only with the aid of further halogen (bromine)-containing substances.        
Existing uses of foamed, siloxane-containing compositions in the apparel segment have been confined to specialty pieces, as for example laminates, with methods ofproduction that are highly costly and inconvenient overall. For instance, JP 7292504 A2, directed only to the production of swimming caps, applies a silicone foam preform to thermoplastic. KR20010077825 A prefoams a silicone onto wax paper and bonds it to a textile with a previously applied adhesive silicone coating in order to obtain a type of synthetic leather. JP 63282381 A2 takes a similarly arduous route in bonding silicone foam to textile using peroxide-crosslinked (and hence intensely odorous) solid silicone. GB 1273468 A makes reference, inter alia, to silicone foam for laminates which are subsequently impregnated with resin. DE 41 01 884 A1, finally, refers to foam of room-temperature-crosslinking (and therefore very slow) RTV silicone, which is sprayed onto textile.
All of the methods practiced and referred to in the prior art, and all of the claimed materials—including the applications, materials, and methods that are common knowledge, as known from CR—have the following drawbacks in common:                use of controversial (odor, residues) or low-efficiency (RTV) blowing agents;        uneconomic operations which also contain sources of error, either as a result of costly and inconvenient multistep methods and/or through the use of siloxanes that are slow to crosslink.        